FIGURE 1.

ABC fails to trigger direct innate immune activation in human monocytes but dose-dependently induces IL-1β release upon TPA or TLR priming. A and B, THP1 cells were directly stimulated with the indicated ABC concentrations, LPS (100 ng/ml), or medium (ctrl) for 16 h (A), or stimulated for 16 h with medium (ctrl), ABC or ATP (5 mm) after priming with medium, 100 nm TPA (+TPA), or 100 ng/ml LPS (+LPS) (B), respectively. A, IL-8 ELISA; B, IL-1β ELISA of culture supernatants. C, IL-1β ELISAs of supernatants from medium- or LPS-primed (5 h, 100 ng/ml) primary human monocytes stimulated with 0.5 mg/ml ABC, 5 mm ATP, or medium (ctrl) for 16 h. D, IL-1β ELISAs of supernatants (SN) from THP1 that were pre-incubated with medium or the indicated TLR8 agonists CL075 (5 μg/ml) or VTX-2337 (10 μm) for 16 h and after 8 h of incubation in TLR8 agonist-free medium stimulated with 0.5 mg/ml ABC or medium for an additional 16 h, respectively. The immunoblots shown are representative of n = 3 experiments; bar diagrams represent mean cytokine concentrations ± S.D. from n ≥ 3 experiments. Statistical differences to the respective experimental controls (unstimulated cells in A and primed controls in B–D) are indicated by asterisks (**, p < 0.01, ***, p < 0.001, n.s. (non-significant) p > 0.05, one-way ANOVA (A) or two-way ANOVA (B–D) with Dunnett's (A and B) or Sidak's (C and D) multiplicity correction).